This invention generally relates to passenger conveyors. More particularly, this invention relates to a device for automatically adjusting the length of a passenger conveyor handrail.
Passenger conveyors typically include a plurality of steps that move in a continuous pattern along a pathway to carry passengers from one landing to another. A handrail typically includes a steel-reinforced belt that travels along side the steps. A drive mechanism typically moves the handrail belt so that it travels along the pathway at the same speed as the steps.
One challenge presented by such handrail assemblies is maintaining an appropriate length of the handrail belt to achieve smooth operation. Common practice has been to provide a single length compensation station on one side of the handrail drive mechanism. While these tension stations have proven useful, they are not without shortcomings and drawbacks.
One major shortcoming of conventional length compensation stations is that they must be manually set to a desired length. Therefore, conventional arrangements cannot accommodate changes in handrail length caused by temperature variations, for example. This requires a mechanic to manually adjust the tension and, therefore, the effective length of the handrail multiple times over the life of the system.
Another conventional arrangement is to use a single tension station to maintain the length of the handrail automatically. The tension station provides a single tension force regardless of which direction the handrail is moving. The force to the handrail must be high enough to bias the handrail (i.e., to maintain the appropriate length) even if the location of the tension station is on the load side of the drive mechanism. This kind of length compensation system is not optimum due to the increased tension on the handrail, which causes heat buildup, undesirable wear and increased power consumption.
There is a need for an improved handrail adjusting device that automatically adjusts the length of the handrail and is responsive to changes caused by temperature variations or a change in the direction of movement of the handrail. This invention provides such a solution and overcomes the shortcomings and drawbacks discussed above.
In general terms, this invention is an automatically adjustable device that provides length compensation for a passenger conveyor handrail to maintain a desired effective length of the handrail. A system designed according to this invention includes a handrail and a drive mechanism that moves the handrail in a selected direction. A first length compensation device is provided on a first side of the drive mechanism that compensates handrail length when the drive mechanism moves the handrail in a first direction. A second length compensation device is positioned on a second side of the drive mechanism that compensates handrail length when the drive mechanism moves the handrail in a second direction.
In one example, the length compensation devices each have a spring loaded arm that bias the handrail between handrail guides such that the effective length of the handrail is adjusted. The tension provided by the spring loaded arm preferably is small enough so that it is automatically overcome whenever the handrail is moved in an opposite direction.
The various features and advantages of the invention will become apparent to those skilled in the art from the following detailed description of the currently preferred embodiments. The drawings accompanying the detailed description can be briefly described as follows.